In recent years, a polymer electrolyte fuel cell has attracted attention as a power generator of an electric vehicle, for example. Examples of such a fuel cell and a separator for a fuel cell are shown in FIG. 7 and FIGS. 8(a) and 8(b).
FIG. 7 is an exploded view showing a configuration of a unit cell constituting a fuel cell 10, and FIG. 8 is a view showing a configuration of a separator 1 for the fuel cell shown in FIG. 7. FIG. 8(a) is a plan view, and FIG. 8(b) is a sectional view taken along line X-Y in FIG. 8(a).
The polymer electrolyte fuel cell 10 is configured such that several tens to several hundreds of MEAs (membrane electrode assemblies) having a solid polymer electrolyte membrane 6, an anode (fuel electrode) 7, and a cathode (oxidant electrode) 8 that are joined via a gasket 9 by two separators 1 for a fuel cell are provided side by side as unit cells, and such that electric current is extracted from an external circuit by supplying fuel gas (hydrogen gas), which is fluid, to the anode 7, and oxidizing gas (oxygen gas), which is fluid, to the cathode 8.
The separator 1 for a fuel cell, as shown in FIGS. 8(a), 8(b), has a shape having a plurality of grooves for gas supply and discharge 11 in one face or both faces of a thin-plate-like body, openings 12 for supplying the fuel gas or the oxidizing gas to the grooves for gas supply and discharge 11, and fixing holes 13 for providing the MEAs side by side, and the separator 1 for a fuel cell has a function of separating the fuel gas and the oxidizing gas flowing through the fuel cell so as to prevent them from mixing of these gases, and takes an important role of transmitting electric energy generated in the MEAs to the outside and radiating heat generated in the MEAs to the outside.
Therefore, properties required of the separator 1 for a fuel cell include having sufficient strength against fastening of a bolt during assembly or against vibration of an automobile or the like, reducing electrical resistance in order to reduce power generation loss, and gas impermeability for completely separating the fuel gas and the oxidizing gas in both of the faces and supplying them to the electrodes.
For such a separator 1 for a fuel cell, a carbon composite material using as a binder a thermosetting resin having advantages in production and cost has been suggested (for example, see patent literatures 1, 2, 3, etc.).